1. Field of the Invention
The present invention relates to improvements during an airbag restraint system for protecting a vehicle passenger in a vehicle serious collision or the like, and more particularly to a configuration of a cover member for a folded airbag.
2. Description of the Prior Art
Hitherto a variety of airbag restraint systems for automotive vehicles have been proposed and put into practical use in order to protect a vehicle passenger in the event of a vehicle serious collision or the like. Such airbag restraint systems are disclosed, for example, in Japanese Patent Publication No. 56-43890 and Japanese Utility Model Provisional Publication No. 61-185642.
The airbag restraint system includes an airbag which is momentarily inflated by being filled with gas from a gas generator. The airbag and the gas generator are fixedly connected to a base plate which is secured to a part of a vehicular body such as an instrument panel or steering wheel. The airbag has a gas passage through which gas from the gas generator is flowed in the airbag. The airbag is usually folded and covered with a cover member made of a plastic so that the airbag does not contact the vehicular body such as a part of the instrumental panel. The peripheral end portion of the cover member is fixedly secured to the end portion of the base plate with rivets or blots. The upper surface of the cover member is formed to be broken at its thin part in the event of the inflation of the airbag so that the airbag is smoothly inflated.
However, difficulties have been encountered in the conventional airbag restraint system, in that the cover member tends to be broken at its peripheral portion which is secured to the base plate by rivets while also being broken at its thin portion in the event of the inflation of the airbag. This causes a problem in that the cover member is broken into several pieces which are scattered in various directions. In order to prevent the cover member from being scattered as mentioned above, another system is disclosed, for example, in Japanese Patent Provisional Publication No. 1-109146. In this system, in order to prevent a cover member from breaking away from a base plate, the cover member is bulged at its periphery and is put between the base plate and a reinforcing plate at an inner side portion of the bulged end while being secured with rivets. However, this system is not sufficient in strength in the event of the inflation of the airbag body since the bulged end is free and tends to be deformed.